Preheat your oven to 350°F (175°C) and prepare your 8×8-inch baking pan by lining it with parchment paper.

Melt unsalted butter in a small saucepan over low heat, then cool slightly.

In a mixing bowl, whisk together the melted butter and light brown sugar until smooth. Add eggs one at a time, whisking well, then stir in vanilla and almond extracts.

In a separate bowl, combine all-purpose flour, baking powder, and salt. Fold this dry mixture into the wet ingredients, being careful not to overmix.

Prepare the frangipane filling by mixing almond flour, granulated sugar, and one egg until smooth.

Spread the blondie batter in the baking pan, dollop the frangipane over it, and swirl with a knife.

Sprinkle sliced almonds on top and press them down slightly.

Bake for 30-35 minutes until golden brown and a toothpick inserted comes out with moist crumbs.

Allow to cool in the pan, then dust with powdered sugar, cut into squares, and serve.